Anionic surfactants are mixed with other surfactant or a builder to be used in laundry detergents and kitchen detergents, foaming agents for toothpaste, emulsifiers for medicines and cosmetics, and other detergents.
There have been known forms of an anionic surfactant, including granule produced by drying an aqueous solution, slurry, or paste of an anionic surfactant (hereinafter, simply referred to as the aqueous solution group of anionic surfactant), and products therefrom such as powder, needle, noodle, and flake. A conventional method for producing an anionic surfactant granule includes drying an aqueous solution etc. of an anionic surfactant as a starting material to remove water, and then optionally processing a dried product by a secondary processing such as crushing and granulating.
Conventional methods for producing an anionic surfactant granule include, for example, spray-drying such as a method of spray-drying a low concentration slurry containing water in an amount of 60 to 70% by weight (JP-A55-69698 and JP-A53-39037) and a method of spray-drying a high concentration slurry of an alkylsulfate having a solid content of 60 to 80% by weight (JP-A54-106428). JP-A2-222498 discloses a method of drying a high concentration paste raw material for detergent containing water in an amount of 20 to 35% by weight with a vacuum thin film dryer.